Wang L V, Jacques S L
Optical Imaging Laboratory, Biomedical Engineering Program, Texas A and M University, College Station 77843-3120, USA.
Comput Methods Programs Biomed. 2000 Mar;61(3):163-70. doi: 10.1016/s0169-2607(99)00041-3.
Diffusion theory and similarity relations were used to calculate the optical diffuse reflectance of an infinitely narrow laser beam incident upon a semi-infinite turbid medium. The results were analyzed by comparison with the accurate results from Monte Carlo simulations. Because a large number of photon packets were traced, the variance of the results from Monte Carlo simulations was small enough to reveal the detailed defects of the diffusion theory and the similarity relations, which are broadly used in photomedicine. We demonstrated that both diffusion theory and similarity relations provide very accurate results when the photon sources are isotropic and buried more deeply than one transport mean free path in turbid media. We found that the key factor affecting the accuracy of the diffusion theory application was the conversion from the infinitely narrow laser beam to an isotropic point source in turbid media.
扩散理论和相似关系被用于计算无限窄激光束入射到半无限浑浊介质上的光学漫反射率。通过与蒙特卡罗模拟的精确结果进行比较来分析这些结果。由于追踪了大量光子包，蒙特卡罗模拟结果的方差足够小，能够揭示扩散理论和相似关系中存在的详细缺陷，而这些理论在光医学中被广泛应用。我们证明，当光子源是各向同性的且埋入浑浊介质的深度超过一个输运平均自由程时，扩散理论和相似关系都能提供非常精确的结果。我们发现，影响扩散理论应用准确性的关键因素是在浑浊介质中将无限窄激光束转换为各向同性点源。
